Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is
none, oncePerWeek, severalPerWeek
or daily.
Build a proper factor for the responses below and store it in a variable
w.
Print the factor.
Write the code to count the numbers of occurrences of each level and
print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek oncePerWeek <NA> none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 × 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the
results.
Next, understand why an error is generated and use replace
argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor
w from it.
Finally, count the numbers of occurrences of each level in
w.
Ensure, that levels are in order provided in the variable
lvs.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "daily" "severalPerWeek" "none"
sample( lvs, 3 )
[1] "daily" "oncePerWeek" "severalPerWeek"
sample( lvs, 3 )
[1] "none" "severalPerWeek" "oncePerWeek"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] severalPerWeek none oncePerWeek none none none severalPerWeek none severalPerWeek severalPerWeek daily
[12] daily none severalPerWeek oncePerWeek oncePerWeek none oncePerWeek daily daily oncePerWeek oncePerWeek
[23] daily severalPerWeek none daily severalPerWeek severalPerWeek none none severalPerWeek none none
[34] none daily severalPerWeek none severalPerWeek none none oncePerWeek daily oncePerWeek daily
[45] none severalPerWeek daily none none none oncePerWeek daily none none none
[56] daily oncePerWeek severalPerWeek severalPerWeek severalPerWeek daily daily daily severalPerWeek none oncePerWeek
[67] daily oncePerWeek oncePerWeek daily severalPerWeek oncePerWeek daily severalPerWeek oncePerWeek daily daily
[78] oncePerWeek none severalPerWeek oncePerWeek none none oncePerWeek oncePerWeek oncePerWeek oncePerWeek daily
[89] daily none severalPerWeek none severalPerWeek none severalPerWeek severalPerWeek severalPerWeek oncePerWeek daily
[100] oncePerWeek
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 × 2
f n
<fct> <int>
1 none 30
2 oncePerWeek 23
3 severalPerWeek 24
4 daily 23
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its
levels.
The factor w from the previous exercise will be then shown
in this order: none, oncePerWeek,
severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed:
daily, severalPerWeek,
oncePerWeek, none.
Apply to w one of the fct_ functions from the
tidyverse library to produce a factor w2 with
the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and
compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 × 2
f n
<fct> <int>
1 daily 23
2 severalPerWeek 24
3 oncePerWeek 23
4 none 30